RESUMO
Tuberculosis (TB) in humans is characterized by formation of immune-rich granulomas in infected tissues, the architecture and composition of which are thought to affect disease outcome. However, our understanding of the spatial relationships that control human granulomas is limited. Here, we used multiplexed ion beam imaging by time of flight (MIBI-TOF) to image 37 proteins in tissues from patients with active TB. We constructed a comprehensive atlas that maps 19 cell subsets across 8 spatial microenvironments. This atlas shows an IFN-γ-depleted microenvironment enriched for TGF-ß, regulatory T cells and IDO1+ PD-L1+ myeloid cells. In a further transcriptomic meta-analysis of peripheral blood from patients with TB, immunoregulatory trends mirror those identified by granuloma imaging. Notably, PD-L1 expression is associated with progression to active TB and treatment response. These data indicate that in TB granulomas, there are local spatially coordinated immunoregulatory programs with systemic manifestations that define active TB.
Assuntos
Granuloma/imunologia , Tuberculose/imunologia , Antígeno B7-H1/imunologia , Células Cultivadas , Citocinas/imunologia , Perfilação da Expressão Gênica/métodos , Humanos , Indolamina-Pirrol 2,3,-Dioxigenase/imunologia , Pulmão/imunologia , Mycobacterium tuberculosis/imunologia , Células Mieloides/imunologiaRESUMO
The current study reveals that in chronic TB, the B cell-deficient µMT strain, relative to wild-type (WT) C57BL/6 mice, displays in the lungs lower levels of inflammation that are associated with decreased CD4+ T cell proliferation, diminished Th1 response, and enhanced levels of interleukin (IL)-10. The latter result raises the possibility that B cells may restrict lung expression of IL-10 in chronic TB. These observations are recapitulated in WT mice depleted for B cells using anti-CD20 antibodies. IL-10 receptor (IL-10R) blockade reverses the phenotypes of decreased inflammation and attenuated CD4+ T cell responses in B cell-depleted mice. Together, these results suggest that in chronic murine TB, B cells, by virtue of their capacity to restrict expression of the anti-inflammatory and immunosuppressive IL-10 in the lungs, promote the development of a robust protective Th1 response, thereby optimizing anti-TB immunity. This vigorous Th1 immunity and restricted IL-10 expression may, however, allow the development of inflammation to a level that can be detrimental to the host. Indeed, decreased lung inflammation observed in chronically infected B cell-deficient mice, which exhibit augmented lung IL-10 levels, is associated with a survival advantage relative to WT animals. Collectively, the results reveal that in chronic murine TB, B cells play a role in modulating the protective Th1 immunity and the anti-inflammatory IL-10 response, which results in augmentation of lung inflammation that can be host-detrimental. Intriguingly, in tuberculous human lungs, conspicuous B cell aggregates are present in close proximity to tissue-damaging lesions manifesting necrosis and cavitation, suggesting the possibility that in human TB, B cells may contribute to the development of exacerbated pathology that is known to promote transmission. Since transmission is a major hindrance to TB control, investigating into whether B cells can shape the development of severe pulmonic pathological responses in tuberculous individuals is warranted.
Assuntos
Mycobacterium tuberculosis , Tuberculose Pulmonar , Tuberculose , Camundongos , Humanos , Animais , Interleucina-10/metabolismo , Camundongos Endogâmicos C57BL , Inflamação , Células Th1RESUMO
Post-tuberculosis (TB) lung disease (PTLD) is increasingly recognized as a major contributor to the global burden of chronic lung disease, with recent estimates indicating that over half of TB survivors have impaired lung function after successful completion of TB treatment. However, the pathologic mechanisms that contribute to PTLD are not well understood, thus limiting the development of therapeutic interventions to improve long-term outcomes after TB. This report summarizes the work of the "Pathogenesis and Risk Factors Committee" for the Second International Post-Tuberculosis Symposium, which took place in Stellenbosch, South Africa in April 2023. The committee first identified six areas with high translational potential: (1) tissue matrix destruction, including the role of matrix metalloproteinase dysregulation and neutrophil activity, (2) fibroblasts and profibrotic activity, (3) granuloma fate and cell death pathways, (4) mycobacterial factors including pathogen burden, (5) animal models, and (6) the impact of key clinical risk factors including HIV, diabetes, smoking, malnutrition, and alcohol. We share here the key findings from a literature review of those areas, highlighting knowledge gaps and areas where further research is needed.
RESUMO
In order to sustain a persistent infection, Mycobacterium tuberculosis (Mtb) must adapt to a changing environment that is shaped by the developing immune response. This necessity to adapt is evident in the flexibility of many aspects of Mtb metabolism, including a respiratory chain that consists of two distinct terminal cytochrome oxidase complexes. Under the conditions tested thus far, the bc1/aa3 complex appears to play a dominant role, while the alternative bd oxidase is largely redundant. However, the presence of two terminal oxidases in this obligate pathogen implies that respiratory requirements might change during infection. We report that the cytochrome bd oxidase is specifically required for resisting the adaptive immune response. While the bd oxidase was dispensable for growth in resting macrophages and the establishment of infection in mice, this complex was necessary for optimal fitness after the initiation of adaptive immunity. This requirement was dependent on lymphocyte-derived interferon gamma (IFNγ), but did not involve nitrogen and oxygen radicals that are known to inhibit respiration in other contexts. Instead, we found that ΔcydA mutants were hypersusceptible to the low pH encountered in IFNγ-activated macrophages. Unlike wild type Mtb, cytochrome bd-deficient bacteria were unable to sustain a maximal oxygen consumption rate (OCR) at low pH, indicating that the remaining cytochrome bc1/aa3 complex is preferentially inhibited under acidic conditions. Consistent with this model, the potency of the cytochrome bc1/aa3 inhibitor, Q203, is dramatically enhanced at low pH. This work identifies a critical interaction between host immunity and pathogen respiration that influences both the progression of the infection and the efficacy of potential new TB drugs.
Assuntos
Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Evasão da Resposta Imune/fisiologia , Mycobacterium tuberculosis/imunologia , Tuberculose/imunologia , Adaptação Fisiológica/fisiologia , Animais , Humanos , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/microbiologia , Camundongos , Mycobacterium tuberculosis/enzimologiaRESUMO
The ubiquitous gasotransmitter hydrogen sulfide (H2S) has been recognized to play a crucial role in human health. Using cystathionine γ-lyase (CSE)-deficient mice, we demonstrate an unexpected role of H2S in Mycobacterium tuberculosis (Mtb) pathogenesis. We showed that Mtb-infected CSE-/- mice survive longer than WT mice, and support reduced pathology and lower bacterial burdens in the lung, spleen, and liver. Similarly, in vitro Mtb infection of macrophages resulted in reduced colony forming units in CSE-/- cells. Chemical complementation of infected WT and CSE-/- macrophages using the slow H2S releaser GYY3147 and the CSE inhibitor DL-propargylglycine demonstrated that H2S is the effector molecule regulating Mtb survival in macrophages. Furthermore, we demonstrate that CSE promotes an excessive innate immune response, suppresses the adaptive immune response, and reduces circulating IL-1ß, IL-6, TNF-α, and IFN-γ levels in response to Mtb infection. Notably, Mtb infected CSE-/- macrophages show increased flux through glycolysis and the pentose phosphate pathway, thereby establishing a critical link between H2S and central metabolism. Our data suggest that excessive H2S produced by the infected WT mice reduce HIF-1α levels, thereby suppressing glycolysis and production of IL-1ß, IL-6, and IL-12, and increasing bacterial burden. Clinical relevance was demonstrated by the spatial distribution of H2S-producing enzymes in human necrotic, nonnecrotic, and cavitary pulmonary tuberculosis (TB) lesions. In summary, CSE exacerbates TB pathogenesis by altering immunometabolism in mice and inhibiting CSE or modulating glycolysis are potential targets for host-directed TB control.
Assuntos
Carbono/metabolismo , Cistationina gama-Liase/fisiologia , Sulfeto de Hidrogênio/toxicidade , Mycobacterium tuberculosis/imunologia , Tuberculose Pulmonar/etiologia , Alcinos/farmacologia , Animais , Cistationina gama-Liase/antagonistas & inibidores , Citocinas/metabolismo , Inibidores Enzimáticos/farmacologia , Glicina/análogos & derivados , Glicina/farmacologia , Glicólise , Sulfeto de Hidrogênio/metabolismo , Linfócitos/efeitos dos fármacos , Linfócitos/imunologia , Linfócitos/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mycobacterium tuberculosis/efeitos dos fármacos , Células Mieloides/efeitos dos fármacos , Células Mieloides/imunologia , Células Mieloides/metabolismo , Transdução de Sinais , Tuberculose Pulmonar/metabolismo , Tuberculose Pulmonar/patologiaRESUMO
The emergence of multi-drug (MDR-TB) and extensively-drug resistant tuberculosis (XDR-TB) is a major threat to the global management of tuberculosis (TB) worldwide. New chemical entities are of need to treat drug-resistant TB. In this study, the mode of action of new, potent quinazoline derivatives was investigated against Mycobacterium tuberculosis (M. tb). Four derivatives 11626141, 11626142, 11626252 and 11726148 showed good activity (MIC ranging from 0.02-0.09 µg/mL) and low toxicity (TD50 ≥ 5µg/mL) in vitro against M. tb strain H37Rv and HepG2 cells, respectively. 11626252 was the most selective compound from this series. Quinazoline derivatives were found to target cytochrome bc1 by whole-genome sequencing of mutants selected with 11626142. Two resistant mutants harboured the transversion T943G (Trp312Gly) and the transition G523A (Gly175Ser) in the cytochrome bc1 complex cytochrome b subunit (QcrB). Interestingly, a third mutant QuinR-M1 contained a mutation in the Rieske iron-sulphur protein (QcrA) leading to resistance to quinazoline and other QcrB inhibitors, the first report of cross-resistance involving QcrA. Modelling of both QcrA and QcrB revealed that all three resistance mutations are located in the stigmatellin pocket, as previously observed for other QcrB inhibitors such as Q203, AX-35, and lansoprazole sulfide (LPZs). Further analysis of the mode of action in vitro revealed that 11626252 exposure leads to ATP depletion, a decrease in the oxygen consumption rate and also overexpression of the cytochrome bd oxidase in M. tb. Our findings suggest that quinazoline-derived compounds are a new and attractive chemical entity for M. tb drug development targeting two separate subunits of the cytochrome bc1 complex.
Assuntos
Antituberculosos/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Complexo III da Cadeia de Transporte de Elétrons/antagonistas & inibidores , Mycobacterium tuberculosis/efeitos dos fármacos , Quinazolinas/farmacologia , Tuberculose Resistente a Múltiplos Medicamentos/microbiologia , Antituberculosos/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Farmacorresistência Bacteriana , Complexo III da Cadeia de Transporte de Elétrons/genética , Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Humanos , Testes de Sensibilidade Microbiana , Mutação , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/metabolismo , Quinazolinas/química , Tuberculose Resistente a Múltiplos Medicamentos/tratamento farmacológicoRESUMO
Rationale: Our current understanding of tuberculosis (TB) pathophysiology is limited by a reliance on animal models, the paucity of human TB lung tissue, and traditional histopathological analysis, a destructive two-dimensional approach that provides limited spatial insight. Determining the three-dimensional (3D) structure of the necrotic granuloma, a characteristic feature of TB, will more accurately inform preventive TB strategies.Objectives: To ascertain the 3D shape of the human tuberculous granuloma and its spatial relationship with airways and vasculature within large lung tissues.Methods: We characterized the 3D microanatomical environment of human tuberculous lungs by using micro computed tomography, histopathology, and immunohistochemistry. By using 3D segmentation software, we accurately reconstructed TB granulomas, vasculature, and airways in three dimensions and confirmed our findings by using histopathology and immunohistochemistry.Measurements and Main Results: We observed marked heterogeneity in the morphology, volume, and number of TB granulomas in human lung sections. Unlike depictions of granulomas as simple spherical structures, human necrotic granulomas exhibit complex, cylindrical, branched morphologies that are connected to the airways and shaped by the bronchi. The use of 3D imaging of human TB lung sections provides unanticipated insight into the spatial organization of TB granulomas in relation to the airways and vasculature.Conclusions: Our findings highlight the likelihood that a single, structurally complex lesion could be mistakenly viewed as multiple independent lesions when evaluated in two dimensions. In addition, the lack of vascularization within obstructed bronchi establishes a paradigm for antimycobacterial drug tolerance. Lastly, our results suggest that bronchogenic spread of Mycobacterium tuberculosis reseeds the lung.
Assuntos
Granuloma/diagnóstico por imagem , Pulmão/diagnóstico por imagem , Pulmão/patologia , Pulmão/ultraestrutura , Tuberculose Pulmonar/diagnóstico por imagem , Tuberculose Pulmonar/microbiologia , Tuberculose Pulmonar/fisiopatologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Imageamento Tridimensional/métodos , Masculino , Pessoa de Meia-Idade , Mycobacterium tuberculosis/patogenicidade , África do Sul , Microtomografia por Raio-X/métodosRESUMO
High attrition rates in tuberculosis (TB) drug development have been largely attributed to safety, which is likely due to the use of endpoint assays measuring cell viability to detect drug cytotoxicity. In drug development for cancer, metabolic, and neurological disorders and for antibiotics, cytotoxicity is increasingly being assessed using extracellular flux (XF) analysis, which measures cellular bioenergetic metabolism in real time. Here, we adopt the XF platform to investigate the cytotoxicity of drugs currently used in TB treatment on the bioenergetic metabolism of HepG2 cells, THP-1 macrophages, and human monocyte-derived macrophages (hMDMs). We found that the XF analysis reveals earlier drug-induced effects on the cells' bioenergetic metabolism prior to cell death, measured by conventional viability assays. Furthermore, each cell type has a distinct response to drug treatment, suggesting that more than one cell type should be considered to examine cytotoxicity in TB drug development. Interestingly, chemically unrelated drugs with different modes of action on Mycobacterium tuberculosis have similar effects on the bioenergetic parameters of the cells, thus discouraging the prediction of potential cytotoxicity based on chemical structure and mode of action of new chemical entities. The clustering of the drug-induced effects on the hMDM bioenergetic parameters are reflected in the clustering of the effects of the drugs on cytokine production in hMDMs, demonstrating concurrence between the effects of the drugs on the metabolism and functioning of the macrophages. These findings can be used as a benchmark to establish XF analysis as a new tool to assay cytotoxicity in TB drug development.
Assuntos
Mycobacterium tuberculosis , Tuberculose , Antituberculosos/toxicidade , Metabolismo Energético , Humanos , MacrófagosRESUMO
The mechanisms whereby Mycobacterium tuberculosis (Mtb) rewires the host metabolism in vivo are surprisingly unexplored. Here, we used three high-resolution mass spectrometry platforms to track altered lung metabolic changes associated with Mtb infection of mice. The multiplatform data sets were merged using consensus orthogonal partial least squares-discriminant analysis (cOPLS-DA), an algorithm that allows for the joint interpretation of the results from a single multivariate analysis. We show that Mtb infection triggers a temporal and progressive catabolic state to satisfy the continuously changing energy demand to control infection. This causes dysregulation of metabolic and oxido-reductive pathways culminating in Mtb-associated wasting. Notably, high abundances of trimethylamine-N-oxide (TMAO), produced by the host from the bacterial metabolite trimethylamine upon infection, suggest that Mtb could exploit TMAO as an electron acceptor under anaerobic conditions. Overall, these new pathway alterations advance our understanding of the link between Mtb pathogenesis and metabolic dysregulation and could serve as a foundation for new therapeutic intervention strategies. Mass spectrometry data has been deposited in the Metabolomics Workbench repository (data-set identifier: ST001328).
Assuntos
Mycobacterium tuberculosis , Tuberculose , Animais , Pulmão , Espectrometria de Massas , Metaboloma , CamundongosRESUMO
New therapeutics to augment current approaches and shorten treatment duration are of critical importance for combating tuberculosis (TB), especially those with novel mechanisms of action to counter the emergence of drug-resistant TB. Host-directed therapy (HDT) offers a novel strategy with mechanisms that include activating immune defense mechanisms or ameliorating tissue damage. These and related concepts will be discussed along with issues that emerged from the workshop organized by the Stop TB Working Group on New Drugs, held at the Gordon Research Conference for Tuberculosis Drug Development in Lucca, Italy in June 2017, titled "Strategic Discussion on Repurposing Drugs & Host Directed Therapies for TB." In this review, we will highlight recent data regarding drugs, pathways, and concepts that are important for successful development of HDTs for TB.
Assuntos
Antituberculosos/uso terapêutico , Desenvolvimento de Medicamentos/métodos , Tuberculose/tratamento farmacológico , Antituberculosos/farmacologia , Humanos , Mycobacterium tuberculosis/efeitos dos fármacos , Tuberculose/imunologia , Tuberculose Resistente a Múltiplos Medicamentos/tratamento farmacológico , Tuberculose Resistente a Múltiplos Medicamentos/imunologiaRESUMO
To facilitate survival under drug stresses, a small population of Mycobacterium tuberculosis can tolerate bactericidal concentrations of drugs without genetic mutations. These drug-tolerant mycobacteria can be induced by environmental stresses and contribute to recalcitrant infections. However, mechanisms underlying the development of drug-tolerant mycobacteria remain obscure. Herein, we characterized a regulatory pathway which is important for the tolerance to isoniazid (INH) in Mycobacterium smegmatis. We found that the RNA polymerase binding protein RbpA associates with the stress response sigma factor σB , to activate the transcription of ppk1, the gene encoding polyphosphate kinase. Subsequently, intracellular levels of inorganic polyphosphate increase to promote INH-tolerant mycobacteria. Interestingly, σB and ppk1 expression varied proportionately in mycobacterial populations and positively correlated with tolerance to INH in individual mycobacteria. Moreover, sigB and ppk1 transcription are both induced upon nutrient depletion, a condition that stimulates the formation of INH-tolerant mycobacteria. Over-expression of ppk1 in rbpA knockdown or sigB deleted strains successfully restored the number of INH-tolerant mycobacteria under both normal growth and nutrient starved conditions. These data suggest that RbpA and σB regulate ppk1 expression to control drug tolerance both during the logarithmic growth phase and under the nutrition starved conditions.
Assuntos
Proteínas de Bactérias/metabolismo , Isoniazida/farmacologia , Mycobacterium smegmatis/metabolismo , Mycobacterium tuberculosis/metabolismo , Polifosfatos/metabolismo , Fator sigma/metabolismo , Antituberculosos/farmacologia , Proteínas de Bactérias/genética , Farmacorresistência Bacteriana , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Mycobacterium smegmatis/efeitos dos fármacos , Mycobacterium smegmatis/genética , Mycobacterium smegmatis/crescimento & desenvolvimento , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/crescimento & desenvolvimento , Fosfotransferases (Aceptor do Grupo Fosfato)/genética , Fosfotransferases (Aceptor do Grupo Fosfato)/metabolismo , Regiões Promotoras Genéticas , Fator sigma/genéticaRESUMO
[This corrects the article DOI: 10.1371/journal.ppat.1006389.].
RESUMO
Signals modulating the production of Mycobacterium tuberculosis (Mtb) virulence factors essential for establishing long-term persistent infection are unknown. The WhiB3 redox regulator is known to regulate the production of Mtb virulence factors, however the mechanisms of this modulation are unknown. To advance our understanding of the mechanisms involved in WhiB3 regulation, we performed Mtb in vitro, intraphagosomal and infected host expression analyses. Our Mtb expression analyses in conjunction with extracellular flux analyses demonstrated that WhiB3 maintains bioenergetic homeostasis in response to available carbon sources found in vivo to establish Mtb infection. Our infected host expression analysis indicated that WhiB3 is involved in regulation of the host cell cycle. Detailed cell-cycle analysis revealed that Mtb infection inhibited the macrophage G1/S transition, and polyketides under WhiB3 control arrested the macrophages in the G0-G1 phase. Notably, infection with the Mtb whiB3 mutant or polyketide mutants had little effect on the macrophage cell cycle and emulated the uninfected cells. This suggests that polyketides regulated by Mtb WhiB3 are responsible for the cell cycle arrest observed in macrophages infected with the wild type Mtb. Thus, our findings demonstrate that Mtb WhiB3 maintains bioenergetic homeostasis to produce polyketide and lipid cyclomodulins that target the host cell cycle. This is a new mechanism whereby Mtb modulates the immune system by altering the host cell cycle to promote long-term persistence. This new knowledge could serve as the foundation for new host-directed therapeutic discovery efforts that target the host cell cycle.
Assuntos
Mycobacterium tuberculosis/fisiologia , Tuberculose/fisiopatologia , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Feminino , Pontos de Checagem da Fase G1 do Ciclo Celular , Interações Hospedeiro-Patógeno , Humanos , Macrófagos/metabolismo , Macrófagos/microbiologia , Camundongos Endogâmicos BALB C , Mycobacterium tuberculosis/genética , Pontos de Checagem da Fase S do Ciclo Celular , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Tuberculose/metabolismo , Tuberculose/microbiologiaRESUMO
We deleted subunits I (cydA) and II (cydB) of the Mycobacterium tuberculosis cytochrome bd menaquinol oxidase. The resulting ΔcydA and ΔcydAB mutants were hypersusceptible to compounds targeting the mycobacterial bc1 menaquinol-cytochrome c oxidoreductase and exhibited bioenergetic profiles indistinguishable from strains deficient in the ABC-type transporter, CydDC, predicted to be essential for cytochrome bd assembly. These results confirm CydAB and CydDC as potential targets for drugs aimed at inhibiting a terminal respiratory oxidase implicated in pathogenesis.
Assuntos
Citocromos c/efeitos dos fármacos , Complexo IV da Cadeia de Transporte de Elétrons/efeitos dos fármacos , Complexo IV da Cadeia de Transporte de Elétrons/genética , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Antituberculosos/farmacologia , Descoberta de Drogas , Genoma Bacteriano/genética , Testes de Sensibilidade Microbiana , Fosforilação Oxidativa/efeitos dos fármacos , Oxigênio/metabolismo , Consumo de Oxigênio/genética , Deleção de Sequência/genéticaRESUMO
Ergothioneine (EGT) is synthesized in mycobacteria, but limited knowledge exists regarding its synthesis, physiological role, and regulation. We have identified Rv3701c from Mycobacterium tuberculosis to encode for EgtD, a required histidine methyltransferase that catalyzes first biosynthesis step in EGT biosynthesis. EgtD was found to be phosphorylated by the serine/threonine protein kinase PknD. PknD phosphorylates EgtD both in vitro and in a cell-based system on Thr(213). The phosphomimetic (T213E) but not the phosphoablative (T213A) mutant of EgtD failed to restore EGT synthesis in a ΔegtD mutant. The findings together with observed elevated levels of EGT in a pknD transposon mutant during in vitro growth suggests that EgtD phosphorylation by PknD negatively regulates EGT biosynthesis. We further showed that EGT is required in a nutrient-starved model of persistence and is needed for long term infection of murine macrophages.
Assuntos
Ergotioneína/biossíntese , Modelos Biológicos , Mycobacterium tuberculosis/metabolismo , Mycobacterium tuberculosis/patogenicidade , Tuberculose/metabolismo , Animais , Linhagem Celular , Ergotioneína/genética , Camundongos , Mycobacterium tuberculosis/genética , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Tuberculose/genética , Tuberculose/patologiaRESUMO
Pulmonary infections with nontuberculous mycobacteria (P-NTM), such as by Mycobacterium avium complex (M. avium), are increasingly found in the elderly, but the underlying mechanisms are unclear. Recent studies suggest that adaptive immunity is necessary, but not sufficient, for host defense against mycobacteria. Heme oxygenase-1 (HO-1) has been recognized as a critical modulator of granuloma formation and programmed cell death in mycobacterial infections. Old mice (18-21 mo) infected with M. avium had attenuated HO-1 response with diffuse inflammation, high burden of mycobacteria, poor granuloma formation, and decreased survival (45%), while young mice (4-6 mo) showed tight, well-defined granuloma, increased HO-1 expression, and increased survival (95%). To further test the role of HO-1 in increased susceptibility to P-NTM infections in the elderly, we used old and young HO-1+/+ and HO-1-/- mice. The transcriptional modulation of the JAK/STAT signaling pathway in HO-1-/- mice due to M. avium infection demonstrated similarities to infected wild-type old mice with upregulation of SOCS3 and inhibition of Bcl2. Higher expression of SOCS3 with downregulation of Bcl2 resulted in higher macrophage death via cellular necrosis. Finally, peripheral blood monocytes (PBMCs) from elderly patients with P-NTM also demonstrated attenuated HO-1 responses after M. avium stimulation and increased cell death due to cellular necrosis (9.69% ± 2.02) compared with apoptosis (4.75% ± 0.98). The augmented risk for P-NTM in the elderly is due, in part, to attenuated HO-1 responses, subsequent upregulation of SOCS3, and inhibition of Bcl2, leading to programmed cell death of macrophages, and sustained infection.
Assuntos
Heme Oxigenase-1/metabolismo , Infecções por Mycobacterium não Tuberculosas/enzimologia , Mycobacterium avium/fisiologia , Infecções Respiratórias/enzimologia , Idoso , Envelhecimento/patologia , Animais , Morte Celular , Suscetibilidade a Doenças , Regulação Enzimológica da Expressão Gênica , Granuloma/microbiologia , Granuloma/patologia , Heme Oxigenase-1/deficiência , Heme Oxigenase-1/genética , Humanos , Leucócitos Mononucleares/microbiologia , Leucócitos Mononucleares/ultraestrutura , Camundongos Endogâmicos C57BL , Infecções por Mycobacterium não Tuberculosas/genética , Infecções por Mycobacterium não Tuberculosas/patologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Infecções Respiratórias/genética , Proteína 3 Supressora da Sinalização de Citocinas/metabolismo , Transcrição GênicaRESUMO
Mycobacterium tuberculosis (Mtb) is a facultative intracellular pathogen and the second largest contributor to global mortality caused by an infectious agent after HIV. In infected host cells, Mtb is faced with a harsh intracellular environment including hypoxia and the release of nitric oxide (NO) and carbon monoxide (CO) by immune cells. Hypoxia, NO and CO induce a state of in vitro dormancy where Mtb senses these gases via the DosS and DosT heme sensor kinase proteins, which in turn induce a set of â¼47 genes, known as the Mtb Dos dormancy regulon. On the contrary, both iNOS and HO-1, which produce NO and CO, respectively, have been shown to be important against mycobacterial disease progression. In this review, we discuss the impact of O2, NO and CO on Mtb physiology and in host responses to Mtb infection as well as the potential role of another major endogenous gas, hydrogen sulfide (H2S), in Mtb pathogenesis.
Assuntos
Gasotransmissores/fisiologia , Mycobacterium tuberculosis/fisiologia , Tuberculose Pulmonar/metabolismo , Monóxido de Carbono/fisiologia , Humanos , Sulfeto de Hidrogênio/metabolismo , Mycobacterium tuberculosis/genética , Óxido Nítrico/fisiologia , Oxigênio/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Tuberculose Pulmonar/microbiologiaRESUMO
Cigarette smoking enhances oxidative stress and airway inflammation in asthma, the mechanisms of which are largely unknown. Myeloid-derived regulatory cells (MDRC) are free radical producing immature myeloid cells with immunoregulatory properties that have recently been demonstrated as critical regulators of allergic airway inflammation. NO (nitric oxide)-producing immunosuppressive MDRC suppress T-cell proliferation and airway-hyper responsiveness (AHR), while the O2(â¢-) (superoxide)-producing MDRC are proinflammatory. We hypothesized that cigarette smoke (CS) exposure may impact MDRC function and contribute to exacerbations in asthma. Exposure of bone marrow (BM)-derived NO-producing MDRC to CS reduced the production of NO and its metabolites and inhibited their potential to suppress T-cell proliferation. Production of immunoregulatory cytokine IL-10 was significantly inhibited, while proinflammatory cytokines IL-6, IL-1ß, TNF-α and IL-33 were enhanced in CS-exposed BM-MDRC. Additionally, CS exposure increased NF-κB activation and induced BM-MDRC-mediated production of O2(â¢-), via NF-κB-dependent pathway. Intratracheal transfer of smoke-exposed MDRC-producing proinflammatory cytokines increased NF-κB activation, reactive oxygen species and mucin production in vivo and exacerbated AHR in C57BL/6 mice, mice deficient in Type I IFNR and MyD88, both with reduced numbers of endogenous MDRC. Thus CS exposure modulates MDRC function and contributes to asthma exacerbation and identifies MDRC as potential targets for asthma therapy.